To make a model of the eardrum, stretch a piece of plastic wrap over your bowl or pot. Make sure the wrap is on there tight. The plastic wrap represents the eardrum.

Place about 20-30 grains of uncooked rice on the top of the plastic wrap.

Now you need some noise. Hold the cookie sheet close to the plastic wrap. Hit the cookie sheet to create a "big bang" noise and watch the rice grains jump. Now you know how sound causes your eardrum to vibrate, sending messages to your brain about the sounds you're hearing!